Bit weight maintainer for marine earth boring

ABSTRACT

A device for use in marine earth boring that supports that portion of the drill pipe weight which is not desired on the drilling bit. The device comprises a large drum, closed at the top and open at the bottom, which drum is placed in the sea. The drum has a central pipe through which the drill pipe and bit passes. The drum is made to have the buoyancy desired by introducing a definite volume of air into the drum. The drum is locked to the drill pipe by means of conventional bowl-and-slips. As the borehole deepens the drum descends with the pipe, and means, manual or automatic, are provided to keep the volume of air constant. The drum is reset for each new length of drill pipe. The device is adapted for either turbodrilling or rotary drilling.

United States Patent lnventor Homer 1. Henderson [72] 3,204,708 9/1965 Berne 175/6 2220 L k San g 76901 3,359,741 12/1967 Nelson 166/.5 [21] Appl. No. 756,453 3,360,042 12/1967 Marion 166/.6 [22] Filed Aug. 30, 1968 3,369,599 2/1968 Evans 166/.5 [45] Patented J 19, 1971 3,456,745 6/1969 Peri 175 7 Primary Examiner-Marvin A. Champion Assistant Examiner-Richard E. Favreau [54] BIT WEIGHT MAINTAINER FOR MARINE EARTH BORING ABSTRACT: A device for use in marine earth boring that sup- 2 Chums 6 Drawing Flgs' ports that portion of the drill pipe weight which is not desired U.S. on the The device comprises a large drum closed 175/27 at the top and open at the bottom, which drum is placed in the [51] list. Cl E21b 7/12 sea. The drum has a central pipe through which the drill pipe Fleld of Search 6, and asses The drum is made to have the buoyancy desired by introducing a definite volume of air into the drum. The drum is locked to the drill pipe by means of conventional [56] References c'ted bowl-and-slips. As the borehole deepens the drum descends UNITED STATES PATENTS I with the pipe, and means, manual or automatic, are provided 3,017,934 l/ 1962 Rhodes et al. 175/7X to keep the volume of air constant. The drum is reset for each 3,189,105 6/1965 Bates et al. 175/5 new length of drill pipe. The device is adapted for either tur- 3,196,958 7/ 1965 Travers et a1. 166/ .5 bodrilling or rotary drilling.

11 [a ,i I] [5 l 24 i PATENTED JAN] 9 I97! SHEET 1 OF 2 .1 FIGZ INVENTOR.

HOMER l. HENDERSON PATENTEDJAN 1 919?:

SHEET 2 0F 2 Fl 6. 6 INVENTOR HOMER l. HENDERSON rotary drilling'as well asturbodrilling." 1

an" WEIGHT sln'mnsri son 1 BORING DESC O a When ea'rth' 'boringfrom a lloating vessel on the surface of the sea the-rocking and pitching of the vessel due to the seas surface waves-causesthe top of the drilling-mast to oscillate, and since the topof the'mast supports the drilling string of pipe, such oscillationresultsinthe raisingandlowering of the drill pipe and resultant fluctuations'of the pipe weight imposed :upon the drilling'biLjForany typeof bit to drill'efficiently it I mustbe loaded with the optimum weight. Underloading causes abigdecrease in boring efflciency,*while overloading causes bit damage and high drill pipe torque. When a roller bit is overloaded the bit bearings fail prematurely and usually the cuttings are not removed effectively. When a diamond bit is overloadedrthe espose'wdiamonds' bury-:themselves in the earth's formation blocking drilling fluid flow around [the diamonds and the diamonds becomeoverheated and are destroyed. I

An' object of this invention'is to provide a'buoyant device that supports the desireddrill pipe loadand is passive to surface wave motion; This means, if the drillpipe string weighs l$ .000 pounds (in waterland it is'desired that 5,000. pounds be imposed "upon the'bit, that thisdevice supports 10,000 pounds of the load and leaves 5,000 pounds for the bit 'tosup:

Another object-of this invention is toprovide a device that permits the drill pipe to descend uniformlyand in unison with mm: liARTI-l I the bit's drillingratepwhatever that may beswhile simultaneously maintaining the desired'load'on the biL-Such a perfect bit feed has long been sought. 1 g Y Another object-of this invention is to provide an inexpensive device to maintain the proper load on a bit and isadapted for sun another object ofwthisinventionisto provide as airbuoyant device for drill" pipe support inwhich theiv'olumeof 7 air within the'device, hence the buoyancy} is either manually or automatically maintained constant as the the device, deepens.

bodrill string of pipe. This is a manually controlled embodiment. v 1 I FIG. 2 shows an elevational view of a flow indicator.

i FIG. 3 is an elevational view, in section, of the rotary table support, needed when drilling with rotating pipe.

FIG. 4 is an elevational view, in section, of the rotationpreventing. device needed when drilling with rotating pipe. This section is taken on section plane 4-4 of FIG. 5. This FIG. shows only the rotation preventing devices, this to avoid congestion of the FIG.

FIG. 5 is a sectional view taken on the section-plane 55 of FIG. 4. 1

FIG. 6 is an elevational, sectional-view of the automatic components used when the automatic embodiment is desired. With reference to FIG. I. the numeral 10 indicates generally the buoyant, open bottom drum, shown submerged, with an air sectionD. Said air section is of such volume as to support the desired load of drill pipe. The vent tube 18 is set at the required depth D to accomplish this. Compressed air is admitted through tube 19 as shown by the tailless flow arrows 29. Any excess of air is exhausted through vent tube 18. The operator knows when air is being vented by the rotation of the multicolored, very light flow vane 30, at the top of tube 18, as

shown by FIG. 2. As the borehole isdeepened the buoyant "Other objects and a fuller understandingjof'the invention may be had by referrin'g to "thefollowing' description and being maintained at DI,

admitted throughjtu be 29 to compensate for the compression and maintain aconstant air volume. In practice the operator may have aneedle valve, not shown. feeding compressed air into the tube 29 at a slow rate, just enough to keep the flow vane 30 slowly turning,evidencethat the air-wales interface is In the center ofthe drum foam 15. The sole purpose of the flotation foam is to reduce the weightof the drum l0' when in'watei' to facilitate handling,

soif desired, it may beeliminated. p e v v [A sjthe bore hole reaches-the depth whereinthe full length of drill pipe just imposesthe optimum desired load on the bit.

then any subsequent additional lengths. of drill pipe, added as the'bore hol'e deepens, should have their weight absorbed by the buoyant drurn 10. The buoyantdrum is not needed when starting the borehole, but it is usually desired to stabilize the drill pipe. When the critical depth is-reached wherein the total weight'oft'he'drill pipe exceeds theoptimum bit load, then the v'en'ttube 1.8 is inserted in the -uppermost hole I6. Whereupon compressed air is admitted through fill tube'l9 until air flow is indicated at the flow vane 30. The buoyant drum l0 islocked to the drill pipe 23 by the slips Z l. in the slip bowl lll. whenever the drum is buoyantand tends to rise relative to the pipe "23. When air is flowing from the tube 18. the weight on the bit is known to be coi'rect and drilling resumes. Assuming that the drill pipe length is 30 feet. then as this length is drilled down. the drum '10 gets progressively deeper, up to 130 feet deeper.

As thedrum l0 getsdeeper it is necessary to compensate for compression of the air section D," (which is-approximately l6 p.'s; i.a. near theseafs surface and increases to approximately 30 p.s.i.a. at a depth 'of 30 feet) and this-is doneby continuously admitting compressed air as discussed above. i

After the first floitt-supported'length of pipe To add an additional length, drilling'is stopped. the pump is stopped, and if a rotary-type drill the rotary is The connectionatthedrilling'head 24 is broken. a new length of drum gets correspondingly deeper submerged and the air within the buoyant drum is correspondingly compressed. If the drilipipe is added and made u at the drilling head, and to the in-hole pipe string; whereupon the pipe string is ready to resume drilling and the head 24 is in position to support the run drill pipe load. At this time the valve 76, FIG. 6, is opened to exhaust all of the air from the drum to. When the air is exhausted the operator engages the winch which spools the line 22 and the drum to is raised to the sea's surface and adjustments are made to increase the air'section D to support an ad-- ditional length of pipe. The drum 10, is then lowered to slightly below the seas surface, air is introduced into the drum until the required new air section D is reached; this sets the slips 2! and drilling is resumed.

When drilling with aluminumpipe the slips may tend to dig into the-pipe when raising the drumll), in which case a ring somewhat larger than the drill pipe may be inserted in the slip bridle so that the pull on the individual slip lines is not only up,

but also outwardly, at the top of each slip 2l. During drilling the slip line 22 is slack, but not so loose as to permit fouling.

The holes 16 in the tank 11, are shown threaded. as well as the plugs t7 and vent tube fitting 18, but it is much more convenient to make these conventional quick-change fittings.

- FIG. 1 shows an embodiment adapted for turbodrilling with nonrotating dual-tube drill pipe wherein 24 is the ho sting head, having elevator bails 25, a drilling fluid entrance pipe 26 and a drilling fluid outlet pipe 21. The tailed arrows 28 show the direction of drilliiig fluid flow. The surface of the sea is inproper buoyancy is to be maintained compressed air must be within the drum ll.

vertical pipe 13. which pipe hasan inside diameter largeenough topass the drill pipe 13,

' threaded-holes '16. spaced at v v has been drilled down towhere its top" is at theoperators platform it is necessary'to addan additional length if drilling is to continue.

FIGS. 3, 4, and 5 show an adaption to accommodate rotating pipe. FlG. 3 shows the equivalent of a rotary table, with modified slips 21A, rotating slip bowl 33, housing 32 with bearings 34 and 35 to rotatably support the slip bowl within the housing 32. The housing 32 is secured to the drum deck 14. To prevent water invasion of the housing 32 two seals are provided, 36 and 37.

It is necessary to restrain the drum from rotating and this may be done as shown by FIGS. 4 and 5, wherein a square section tubing 39 is positioned over the rotary housing 32 and is secured to the deck 14 by the tubing flange 41. Telescoping within the tubing 39 is a smaller square section tubing 40. The tubing 40 is of such a size that it cannot be rotated within the tubing 39'but is free for longitudinal movement, however it cannot be pulled upward out of the tubing 39 due to its own flange 43 and the tubing 39 flange 42. The smaller tubing carries arms 44 at its upper end towhich arms are secured the antirotation cables 45. The rotational torque is not high being merely the friction of the bearings within the housing 32. The

cables'45 may be secured to the boat or mast as by hooks, or

vertical cables or tracks may be provided on which the terminals of cables 45 can travel vertically while still preventing rotation. The operation of this embodiment is substantially the same as for the nonrotating embodiment. The arms 44 are normally near the operator's platform or the boat deck, with the telescoping feature permitting the drum 10 with the rotary 32 to descend 30 feet as the hole is deepened. To conserve space in some installations it may be desirable to use more than two telescoping tubes in order to use shorter tubes.

Since the slips ZIA-rotate withthe pipe when drilling it would cause a winding-up of the slip line 22 should it be connected directly to the slips 21A. In this embodiment the slips have an extended neckas shown in FIG. 3, which neck extends through a hole in the center of a slip yoke 84. This yoke is a square plate of steel that fits loosely in the tubing 39 to prevent rotation of the yoke. The bridle 22 is secured to the yoke and runs upwardly, exiting through a hole in the centering plate 45 at the top of tubing 40 as shown in FIG. 5.

FIG. 6 shows an embodiment for automatically maintaining a desired section D of compressed air. This embodiment is based upon two rolling diaphragm bellows 46 and 51. The bellows 46 is larger than the bellows 51. The bellows 46 is in the drum 11 and bellows 51 is on the operator's platform or boat deck. Bellows 46 has a means for sensing the depth of air section D by measuring the weight of a lighter-than-water helix of polypropylene rope 63. This weight is transmitted by the beam 61 to the piston rod 49 of the bellows 46 and thence as a pressure through the liquid filled bellows 46 and liquid filled connecting tube 59 to the lower liquid filled portion of the smaller bellows 51. This pressure under the diaphragm 53 of the bellows 51 causes a force on the bellows piston 52, causing it to rise, compressing the spring 55. The amount of pressure, piston force, spring compression and length of rise of the piston 52 and piston rod 54 are directly proportional to the length of the unbuoyed section of the rope 63, whichunbuoyed section is that portion of rope in the air section D.

Thus the extension of the piston rod 54 indicates the section D of air within the drum 10. There is a multiplying factor in the relative movement of piston rod 54, relative to the piston rod 49. Since this is a closed hydraulic system the ratio of this movement is the inverse ratio of piston areas. The calibration on the bracket 66 permits the operator to observe the thickness of section D at any time.

FIG. 6 shows the status of this embodiment when at the sea's surface and with the drum 10 completely water filled, no air section D. The bellows 46 is mounted on a small mounting plate 80, together with a bracket 60, for supporting the beam 61. This small assembly is accommodated in a recess in the flotation foam 15. A hole in the deck 14 is left for insertion of this assembly and this hole is sealed by the mounting plate 80, which plate has sealing dope on the edges of its bottom to effect the seal. The connecting tube 59 is a small ()6 inch) bore flexible tube to facilitate assembly. The plug 77 is removed to fill the bellows-tube assembly with liquid, the liquid being introduced at the plug 78 of the bellows 51 and air allowed to escape at the plug 77. When the system is free of air the plug 77 is reinserted making a tapered thread seal in the wall of the bellows 46 and an O-ring seal between its own head and the mounting plate 80. Of coursethe plug 78 is reseated when the system is full ofliquid. I

It is noted that there is an ele ati orta'l difference E between the upper bellows and the lo wer bellows. Thus the lower bellows experiences a pressure'init s'jupper compartment corresponding to this elevational headand the density of liquid in the system. The lower compartrrien tjof the lower bellows senses the submergence head S since ower'case is open to the sea at the hole 79. The upper case f the upper bellows 51 sees the same air pressure as in the flow tube 19 due to the connecting tube 58. This air pressure is atmospheric when the drum 10 is at the seas surface and the valve 76 is open, as shown. However, when the drum 10 is in operation and air is within the drum, then air surrounds the bellows 46; its lower chamber, the flow tube 19, and the upper chamber of the upper bellows 51, all see the same air pressure. When air is flowing in the tube 19 the tube 58 sees the friction flow loss of head between the bottom of tube 19 and the takeoff location of tube 58. This is a minor difference that an operator soon learns to sense and to compensate for. Even this small difference can be eliminated by running the tube 58 all the way to the bottom of the tube 19.

HO. 6 shows the automatic feature of this embodiment, the control circuit having power supply terminals 71, and the power circuit with power supplyterminals 72. The relay is a normally closed relay. Assume the valve 76 is closed, and the compressor C has the receiver R filled with compressed air. Also that there is no air in drum l0 and it is desiredto put a 2- foot section of air in the drum. If the switch 73 is closed the normally closed solenoid valve 74 opens and air begins to flow into the drum 10. As air displaces the water surrounding the bellows 46 the Z-pound mass of polypropylene head 62 is no longer buoyed by water and becomes aZ-pound weight on the beam 61 which is converted to pressure in the lower compartment of the bellows 51. The 2-pound weight is selected to compensate for the elevational head E and the unbuoyed weight of the drum 10. Polypropylene is selected because it has a specific gravity of 0.90 and is completely buoyed when submerged, with a 10 percent resultant upward force. As the air continuesito enter the drum and the section D of air increases (air-water interface deepens) a portion of the coiled po ypropylene rope 63 becomes air surrounded as the section D increases. The portion of rope in section D is no longer water supported and its weight is imposed upon the beam 61 generating pressure in the bellows system causing the piston 54 to rise in proportion to the weight of rope suspended in air. If the helix of rope has a weight of 1 pound per foot it contributes 1 pound of weight on the beam 61 for each foot of section D. The piston rod 54 rises accordingly. Thus when the section D is 2-feet thick the weight on the outer end of beam 61 is 4 pounds (2 pounds for the head 62, and 2 pounds for the rope in the section D). Therefore the regulating screw 67 is preset at 2 pounds for a 2-foot section of air, and when the air section D reaches 2 feet the piston rod 54 contacts the adjusting screw 67 closing the control circuit 71, which opens the relay 70, causing the closing of the normally closed solenoid valve 74. As drilling progresses and the hole gets deeper, the air section D is compressed due to the greater water head, and the section D decreases the water-air interface rises within the drum submerging some of the rope that had been in section D thereby decreasing the load on the beam 61, resulting in the piston rod 54 receding and opening the control circuit. Thereupon the solenoid valve opens until the air section D is again returned to 2 feet, whereupon the control circuit is again closed, causing the solenoid valve to close.

The polypropylene rope 63 is coiled into a helix with sufficient turns per foot to approximate 1 pound per foot, and four flexible cords 64 are tied as at 81, in orientation to hold the rope in a helix. The lower ends of the tie cords are secured to the four-legged spider bracket 65, and the upper ends are tied to the four pins 82 in the head 62.

The piston rod 54 may have an electrical contact 56, of

silver, and a phosphor bronze spring 69 to permit free vertical travel and to tie it into the electric control circuit 7]. The adjusting screw 67 may also have a silver contact 68.

Should one not need compressed air for other uses, the receiver R may be dispensed with and a low pressure rotary compressor substituted therefore. In such a case the power circuit includes the drive motor for the compressor.

The sensitive, low pressure gauge 75 serves as a check on the air pressurewithin the drum 10. Using this gauge and knowing the depth to the top of the drum 10, (the line 22 can be calibrated), one can compute the depth of the air-water interface in the drum, knowing that the pressure head of sea water is 0.444 p.s.i. per foot of depth. This is especially useful between wave crest and wave valley. This difference of pressure compresses the air within the drum 10 giving slightly lesser buoyancy when the drum is under the crest. hence a tendency to sink. This is ofi'set by the rotary movement of the surface and near-surface water particles during a wave cycle.

' This water movement is upward as the crest approaches and the pressures due to wave crest and wave valley, radiate out as for manual operations. The operator can be supplied depth pressure curves to facilitate evaluations. He can operate without tube 18. a

The tube 19 is preferably a flexible hose, normally spooled on a conventional grooved and swiveled hose reel. This hose should be large enough in diameter to permit rapid flow of air, 1% inches for instance. All of the equipment shown as being above sea level in FIG. 6 would be upstream from the swiveled hose reel.

The tube 59 should be flexible and small in diameter, say inch internal diameter. Also, it would exit from tube 19,

downstream from the hose reel. 4 g y The tube 18 of FIG. 1 should be flexible and smaller in diameter, such as%-inch intemal'diameter. It may be lashed to the larger tube 19.

This equipment is primarily for exploration drilling, with hole depths being less than 3,000 feet, however it can be used for deeper drilling. The buoyant drum 11, may be 5 feet in diameter for shallow (2,000 feet) drilling and the deck 14 may be used as a working platform when it is surfaced. When so used the deck is given a surface of corkto increase its coeffi cient of friction when wet to assure good footing for the workmen. For deeper drilling the drum is increased in diameter.

The calibration on bracket 66 is normally made in an actual sea test. A distance measuring probe is inserted through the tube 19. This probe has exposed electrical electrodes on its lower end which are shorted upon salt-water contact. For various stable settings the extension of the piston rod 54 and the depth of water-air interface are determined and the scale on 66 so marked. Whenever there is no danger of explosive petroleum gas the automatic control device can be simplified by the expedient of two Nichrome resistance wires stretched from top to bottom of the tank 11. The resistance of these wires will vary with the percent of their length shorted by the salt water, which resistance can be very simply be used-to determine the section D, of air, as well as for the control circuit for automatic control. Further, one can use an acoustic distance measuring device for determining the depth of sec tion D.

The drum 10 is substantially passive to wave action when submerged, even when close to the seas surface, provided it is deeper than the valley of the waves. When such is the case there is no buoyancy change due to increase in submerged volume as the wave passes over the drum, radically different from a surfaced supported body. The drum does see the change of pressure due to the difference of submerge'nce hemispheres and quickly become fully compensating.

This invention maybe modified in various respects as will occur to those skilled in the art and the exclusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim:

1. A drill bit weight maintainer for marine earth boring with a marine drilling rig, drill pipe and drill bit comprising:

a buoyant drum, sealed at the top and open at the bottom,

displaced in the sea's water;

an open vertical tube passing through said buoyant drum and integral therewith, to permit passage therethrough of the drill pipe and the drill bit;

means for selectivelylocking said buoyant drum to the drill pipe, thereby transfering its buoyancy to the drill pipe;

a gas exhaust port in said buoyant drum. placed at a predetermined depth below the top of said buoyant drum. at which depth the buoyant drum will have that buoyancy required to support that portion of the drill pipe weight which is not desired on the drill bit. when gas filled above said exhaust port; and g a gas-introducing tube extending from the drilling rig to the top of the buoyant drum for introducing compressed gas into said buoyant drum to maintain, as the buoyant drum sinks deeper and deeper, that said predetermined depth of gas, being the depth of said gas exhaust port.

2. A drill bit weight maintainer for marine earth boring with a marine drilling rig, drill pipe, and drill bit comprising:

a buoyant drum, sealed at the top and open at the bottom,

displaced in the sea's water;

an open vertical tube passing through said buoyant drum and integral therewith, to permit passage therethrough of the drill pipe and the drill bit;

means for selectively locking said buoyant drum to the drill pipe, thereby transfering its buoyancy to the drill pipe;

at gas-depth sensing means within said buoyant drum and responsive to the depth of gas therein;

communicating means between the said gas-depth sensing means and the drilling rig to indicate at the drilling rig the gas depth within said buoyant drum;

a gas-conducting tube extending from top of the buoyant drum; and

gas-admitting means responsive to the said gas-depth sensing means to admit compressedgas into said buoyant drum via the gas-conducting tube to maintain that desired depth of gas in the buoyant drum that will provide in the buoyant drum that buoyancy required to support that portion of the drill pipe weight which is not desired on the drill bit.

the drilling rig to the 

1. A drill bit weight maintainer for marine earth boring with a marine drilling rig, drill pipe and drill bit comprising: a buoyant drum, sealed at the top and open at the bottom, displaced in the sea''s water; an open vertical tube passing through said buoyant drum and integral therewith, to permit passage therethrough of the drill pipe and the drill bit; means for selectively locking said buoyant drum to the drill pipe, thereby transfering its buoyancy to the drill pipe; a gas exhaust port in said buoyant drum placed at a Predetermined depth below the top of said buoyant drum, at which depth the buoyant drum will have that buoyancy required to support that portion of the drill pipe weight which is not desired on the drill bit, when gas filled above said exhaust port; and a gas-introducing tube extending from the drilling rig to the top of the buoyant drum for introducing compressed gas into said buoyant drum to maintain, as the buoyant drum sinks deeper and deeper, that said predetermined depth of gas, being the depth of said gas exhaust port.
 2. A drill bit weight maintainer for marine earth boring with a marine drilling rig, drill pipe, and drill bit comprising: a buoyant drum, sealed at the top and open at the bottom, displaced in the sea''s water; an open vertical tube passing through said buoyant drum and integral therewith, to permit passage therethrough of the drill pipe and the drill bit; means for selectively locking said buoyant drum to the drill pipe, thereby transfering its buoyancy to the drill pipe; a gas-depth sensing means within said buoyant drum and responsive to the depth of gas therein; communicating means between the said gas-depth sensing means and the drilling rig to indicate at the drilling rig the gas depth within said buoyant drum; a gas-conducting tube extending from the drilling rig to the top of the buoyant drum; and gas-admitting means responsive to the said gas-depth sensing means to admit compressed gas into said buoyant drum via the gas-conducting tube to maintain that desired depth of gas in the buoyant drum that will provide in the buoyant drum that buoyancy required to support that portion of the drill pipe weight which is not desired on the drill bit. 